Neuroscience
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A variety of metabotropic excitatory amino acid receptors are present in the thalamus. We have investigated the possibility that some of these receptors may have presynaptic effects on GABAergic inhibitory transmission in the thalamus. Inhibitory responses in ventrobasal thalamic neurons of urethane-anaesthetized rats were evoked by either air-jet stimuli to the vibrissae or by electrical stimulation of the somatosensory cortex. ⋯ As the inhibitory responses arise from the neurons of the nucleus reticularis thalami, some distance away from the site of recording and iontophoretic drug application, it is likely that the reduction of inhibition seen with L-AP4 and CCG1 is due to an action of these agonists on the terminals or axons of these inhibitory neurons. The novel antagonists of L-AP4 and CCG1, alpha-methyl-L-AP4 and alpha-methyl-CCG1, were found to block the disinhibitory actions of the agonists in a differential manner when applied iontophoretically. This suggests that there may be at least two types of receptor mediating the disinhibitory effects.(ABSTRACT TRUNCATED AT 250 WORDS)